Speciesism involves assigning different values or rights, or special consideration, to individuals solely on the basis of their species membership. The term was coined in 1973 by British psychologist Richard D. Ryder to denote prejudice against non-humans based on morally irrelevant physical differences.

The term is mostly used by animal rights advocates, who argue that species membership has no moral significance, and that it is both irrational and morally wrong to regard sentient beings as objects or property. Philosopher Tom Regan argues that all animals have inherent rights and that we cannot assign them a lesser value because of a perceived lack of rationality, while assigning a higher value to infants and the mentally impaired solely on the grounds of membership of a certain species. Peter Singer's philosophical arguments against speciesism are based on the principle of equal consideration of interests.

One argument used to show that speciesism is an arbitrary discrimination is called the argument from marginal cases. This says that if marginal-case human beings – such as infants, the senile, the comatose, and the cognitively disabled – have a certain moral status, then non-human animals must have it too, since there is no morally relevant ability that the marginal-case humans have that non-human animals lack. "Moral status" may include a right not to be killed or made to suffer, or a general moral requirement to be treated in a certain way.

Clinton Richard Dawkins, FRS, FRSL (born 26 March 1941), known as Richard Dawkins, is a British ethologist, evolutionary biologist and author. He is an emeritus fellow of New College, Oxford, and was the University of Oxford's Professor for Public Understanding of Science from 1995 until 2008.

Dawkins came to prominence with his 1976 book The Selfish Gene, which popularised the gene-centered view of evolution and introduced the term meme. In 1982 he introduced an influential concept into evolutionary biology, presented in his book The Extended Phenotype, that the phenotypic effects of a gene are not necessarily limited to an organism's body, but can stretch far into the environment, including the bodies of other organisms.

Dawkins is an atheist, a vice president of the British Humanist Association, and a supporter of the Brights movement. He is well known for his criticism of creationism and intelligent design. In his 1986 book The Blind Watchmaker, he argued against the watchmaker analogy, an argument for the existence of a supernatural creator based upon the complexity of living organisms. Instead, he described evolutionary processes as analogous to a blind watchmaker. He has since written several popular science books, and makes regular television and radio appearances, predominantly discussing these topics. In his 2006 book The God Delusion, Dawkins contends that a supernatural creator almost certainly does not exist and that religious faith is a delusion—"a fixed false belief." As of January 2010 the English-language version has sold more than two million copies and had been translated into 31 languages.